1. Technical Field
The present invention relates to an auto-balancing device, and to a disc chucking device and a disc driving device equipped with the auto-balancing device.
2. Description of the Related Art
Recent developments in electronics have led to the use of high-capacity information storage apparatus, such as the CD (compact disc), DVD (digital versatile disc), BD (Blu-ray disc), HD DVD (high definition DVD), etc. Accordingly, there is also a demand for high-speed rotations in the disc drive, which is a device for operating such storage apparatus.
FIG. 1 is a cross-sectional view of an optical disc drive motor according to the related art. Referring to FIG. 1, the motor 10 may be equipped with a disc chucking device 20. While the motor 10 according to the related art may not provide any problems for rotations at low speeds, but for high speed rotations, the motor 10 may cause serious problems. The centrifugal force acting on a rotating object increases quadratically with respect to the increase in rotation speed. Thus, an increase in the rotation speed of the motor 10 is correlated with an increase in vibration.
The more the rotation speed of the motor 10 is increased, the greater will be the degree of unbalanced centrifugal force, where the resulting vibration may cause difficulty in reading or writing information from or to a disc. Although recent developments in motor-manufacturing techniques have reduced manufacturing tolerances, etc., to increase precision in the products, this is correlated with a rise in manufacturing costs.
A disc chucking device that is equipped with an auto-balancing device to overcome such problems may include multiple correcting balls in a ring-shaped insertion groove. During low-speed rotations, the positions of the correcting balls may be random. After the rotation speed exceeds a certain level, the correcting balls may be distributed evenly across the insertion groove, due to centrifugal forces. In an unbalanced state, the distribution of the correcting balls may be temporarily concentrated in a particular area to resolve this unbalance.
However, at around the resonance point, a phenomenon may occur, in which the correcting balls do not halt within the insertion groove but instead continue to rotate, where this phenomenon is liable to cause problems in operation. Moreover, the correcting balls may act as a dead load in cases where the rotating shaft of the motor forms an angle with the direction of gravity, and problems of noise and vibration may occur during acceleration or deceleration, when the correcting balls collide with one another.
Also, due to an increase in spatial restrictions caused by the trends in current electronic products towards smaller and thinner devices, the annular insertion groove, into which multiple correcting balls may be inserted, may be located near the outer perimeter of the motor. This structure can result in various external forces, caused by an unbalance in the structure, being applied over the entire structure of the motor, as well as in losses in rotational force of the rotor.